>>1 - if they are not indexes, why are they in the sysindexes table and why does SQL tell you it is rebuilding indexes based on their existence as other real indexes are dropped/added?
>
>They're probably implemented using the same mechanism that SQL Server uses to track index statistics.
>
>>2 - whatever they are - do they help in query performance at all?
>
>Yes. Refer to the topic Distribution Statistics and also Create Statistics
>
>-Mike

Thanks Mike!